1. Field of the Invention
This invention relates to a method and apparatus for detecting the direction of incidence of electromagnetic radiation with the help of two optical receiving systems which operate with separate detectors, the outer system being fixed and the inner system being rotatable.
2. Description of the Prior Art
The allowed German patent application No. 1,548,421 discloses a device for detecting electromagnetic radiation and for determining its direction of incidence. Circular sensing is effected with the help of a rotating mirror and an associated first optical receiving system, and this arrangement serves for detecting radiation in the visible and/or infrared range. A further optical receiving system, consisting of laser detectors arranged in a ring, serves for detecting radiation in the laser frequency range. The laser detectors thus surround the optical system approximately in the configuration of a ring, whereby this system serves for detecting the visible and/or infrared radiation range. A device for detecting electromagnetic radiation and for identifying its direction of incidence is disclosed in that a system for an automatic panoramic directional finding for electromagnetic radiation of the visible and/or infrared spectrum range comprises an optical receiving system sensing the horizon by way of rotation, automatic panoramic direction finding being per se well known in the art. The system is placed in a common housing together with several fixed laser radiation detectors which are arranged in a ring about the vertical axis of the rotational optical receiving system, but outside of the range thereof. An indicator is provided for indicating the direction of incidence of the visible and/or infrared radiation, the indicator rotating in synchronism with the rotating optical receiving system and provided with a rotatable member within a compass rose (scale), while an indicator of the direction of incidence of laser radiation is provided upon a ring-shaped scale which is concentric about the compass rose and which is subdivided into sections corresponding to the respective orientation of the different laser detectors.
Since the modern electro-optical locating methods, follow-up methods and search methods to a great extent operate with individual pulses or with pulse trains of very short durations, respectively, it is a fact that search systems which sense the azimuth of a pivotable mirror arrangement do not offer sufficient guarantee that targets are actually detected. Therefore, it must be required in an all-around direction finding arrangement that the arrangement is always ready to receive when a safe target detection is to be guaranteed. On the other hand, such a receiving system continuously searching all around does not provide sufficiently accurate target resolution, or expressed differently, sufficiently accurate detection of the direction of incidence of electromagnetic radiation.